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• Error : Implementation for method missing (Delphi Prism)

  - by Ilya

  I wrote my method: LangChange type MainForm = partial class(System.Windows.Forms.Form) private ... method LangChange(); protected method Dispose(disposing: Boolean); override; public constructor; end; implementation ... method LangChange(); begin ... end; However,I have an error Error 1 (PE33) Implementation for method "Compiler.MainForm.LangChange" missing What is wrong?Help please!

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• How created method with signature as List

  - by London

  Hi all, I'm very new to Java programming language so this is probably dumb question but I have to ask it because I can't figure it out on my own. Here is the deal. I want to create method which extracts certain object type from a list. So the method should receive List as argument, meaning list should contain either Object1 or Object2. I've tried like this : public Object1 extractObject(List<?>){ //some pseudo-code ... loop trough list and check if list item is instance of object one return that instance } The problem with declaring method with List<?> as method argument is that I receive compilation error from eclipse Syntax error on token ">", VariableDeclaratorId expected after this token. How do I set the method signature properly to accept object types either Object1 or Object2 ? Thank you

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• Dynamically find the parameter to be passed as <T> to a generic method

  - by Codex

  A generic method is defined as follows: private static T GetComparisonObject<T>(ComparisonAttribute attribute, object objectToParse) { // Perform a some action return (T)resultObject; } The method is invoked as follows: var srcObjectToCompare = GetComparisonObject<DynamicType>(attributeToCompare, srcObject); The type for which the method needs to be invoked is configured in the config file as: <add attributename ="Count" attributetype ="MemberInformation" attributeparam ="Count" type="System.Int32" comparertype="ditCreditEMGTestAutomationDifferenceEngine.Comparers.TypeComparer, ditCreditEMGTestAutomationDifferenceEngine.dll" /> The token that is passed in < for the generic methods has to be the type for which the method is being invoked. From the type key configuration in the XML, an instance of Type represnting the type can be created{i.e. Type.GetType("System.Int32")}, but how can the Type Definition be generated which can then be passed to the the Generic method? Hope am not missing something elementary here!! :-O Thanks in advance.

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• Confirm delete of record, from method

  - by Melt

  Hi all, How can I pop up a message box to confirm a delete, from inside a method? Normally i would just use the following line in my button: OnClientClick="return confirm('Are you sure you want to delete this comment?');" However this delete method can also be called by a querystring, so I need the confirm message box functionality in the method, please? // delete comment method private void DeleteComment() { int commentid = Int32.Parse(Request.QueryString["c"]); // call our delete method DB.DeleteComment(commentid); } I can't click the button through code, because it doesn't fire the OnClientClick event btnDelete_Click(null, null); Regards Melt

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• Comparing all properties of an object using expression trees

  - by stringargs

  Hi, I'm trying to write a simple generator that uses an expression tree to dynamically generate a method that compares all properties of an instance of a type to the properties of another instance of that type. This works fine for most properties, like int an string, but fails for DateTime? (and presumably other nullable value types). The method: static Delegate GenerateComparer(Type type) { var left = Expression.Parameter(type, "left"); var right = Expression.Parameter(type, "right"); Expression result = null; foreach (var p in type.GetProperties()) { var leftProperty = Expression.Property(left, p.Name); var rightProperty = Expression.Property(right, p.Name); var equals = p.PropertyType.GetMethod("Equals", new[] { p.PropertyType }); var callEqualsOnLeft = Expression.Call(leftProperty, equals, rightProperty); result = result != null ? (Expression)Expression.And(result, callEqualsOnLeft) : (Expression)callEqualsOnLeft; } var method = Expression.Lambda(result, left, right).Compile(); return method; } On a DateTime? property it fails with: Expression of type 'System.Nullable`1[System.DateTime]' cannot be used for parameter of type 'System.Object' of method 'Boolean Equals(System.Object)' OK, so it finds an overload of Equals that expects object. So why can't I pass a DateTime? into that, as it's convertible to object? If I look at Nullable<T>, it indeed has an override of Equals(object o). PS: I realize that this isn't a proper generator yet as it can't deal with null values, but I'll get to that :)

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• Accessing wrapped method attribute in C#

  - by prostynick

  I have following code: public static void ProcessStep(Action action) { //do something here if (Attribute.IsDefined(action.Method, typeof(LogAttribute))) { //do something here [1] } action(); //do something here } For easy use I have some similar methods using method above. For example: public static void ProcessStep(Action<bool> action) { ProcessStep(() => action(true)); //this is only example, don't bother about hardcoded true } But when I use the second method (the one above), even if original action had attribute, code [1] will not be executed. How can I find if method is only wrapper and underlying method contains attribute and how to access this attribute?

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• Are there equivalents to Ruby's method_missing in other languages?

  - by Justin Ethier

  In Ruby, objects have a handy method called method_missing which allows one to handle method calls for methods that have not even been (explicitly) defined: Invoked by Ruby when obj is sent a message it cannot handle. symbol is the symbol for the method called, and args are any arguments that were passed to it. By default, the interpreter raises an error when this method is called. However, it is possible to override the method to provide more dynamic behavior. The example below creates a class Roman, which responds to methods with names consisting of roman numerals, returning the corresponding integer values. class Roman def romanToInt(str) # ... end def method_missing(methId) str = methId.id2name romanToInt(str) end end r = Roman.new r.iv #=> 4 r.xxiii #=> 23 r.mm #=> 2000 For example, Ruby on Rails uses this to allow calls to methods such as find_by_my_column_name. My question is, what other languages support an equivalent to method_missing, and how do you implement the equivalent in your code?

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• Python: Hack to call a method on an object that isn't of its class

  - by cool-RR

  Assume you define a class, which has a method which does some complicated processing: class A(object): def my_method(self): # Some complicated processing is done here return self And now you want to use that method on some object from another class entirely. Like, you want to do A.my_method(7). This is what you'd get: TypeError: unbound method my_method() must be called with A instance as first argument (got int instance instead). Now, is there any possibility to hack things so you could call that method on 7? I'd want to avoid moving the function or rewriting it. (Note that the method's logic does depend on self.) One note: I know that some people will want to say, "You're doing it wrong! You're abusing Python! You shouldn't do it!" So yes, I know, this is a terrible terrible thing I want to do. I'm asking if someone knows how to do it, not how to preach to me that I shouldn't do it.

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• how to call a view method to a model in zendframework

  - by Awais Qarni

  hello I just want to ask whether we can call a view method to a model? I know that we can call it on our controller in zend framework. Like if I want to call the url method of view on my controller I can call it like this $this->view->url(array(),''); and on the view we just can call it by $this->url(array(),''); But When I tried to call the same method on my model by $this->view->url(array(),''); it generates an error of call to undefined method url. Now I want to ask whether it is possible to call view method to a model? If yes then how? What Am I doing wrong. Thanks

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• Forcing a method to be non-transactional in JPA (Eclipselink)

  - by rhinds

  Hi, I am developing an application using Eclipselink and as part of the app I need to be able to manipulate some of the objects which involves changing data without it being persisted to the database (i merging/changing objects for some batch generation processes). I am reluctant to change the data in the Entity objects, as there is a risk that even though i have not marked the methods as @Transactional, this method could in the future be inadvertantly called from within a transactional method and these changes could be persisted. So my question is, is there anyway to get around this? Such as force a method to always be non-transactional regardless; terminate any transactionality as soon as the method is started; etc. I know there is a .detach() method that can detach the objects from the Entity Manager, however, there are many objects and this seems like a potentially error prone fail-safe on my code.

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• how can we call one class's method through another class's object in php

  - by hello

  I want to know that is there any method in PHP by which i can call one class's method from another class object. let me clear here is one class class A() { public function showData(){ //here is method of class A } } // here is another class class B(){ public function getData(){ //some method in class B } } //now i create two objects $objA= new class A(); $objB=new class B(); now i want to call this $objB->showData();<--- is that possible .. by any how method( using public, inheritence,child parent etc...) please help me

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• Retrieving the MethodInfo of of the correct overload of a generic method

  - by Anne

  I have this type that contains two overloads of a generic method. I like to retrieve one of the overloads (with the Func<T> parameter) using reflection. The problem however is that I can't find the correct parameter type to supply the Type.GetMethod(string, Type[]) method with. Here is my class definition: public class Foo { public void Bar<T>(Func<T> f) { } public void Bar<T>(Action<T> a) { } } And this is what I've come up with, unfortunately without succes: [TestMethod] public void Test1() { Type parameterType = typeof(Func<>); var method = typeof(Foo).GetMethod("Bar", new Type[] { parameterType }); Assert.IsNotNull(method); // Fails } How can I get the MethodInfo of a generic method of which I know the parameters?

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• C++ - checking if a class has a certain method at compile time

  - by jetwolf

  Here's a question for the C++ gurus out there. Is there a way to check at compile time where a type has a certain method, and do one thing if it does, and another thing if it doesn't? Basically, I have a template function template <typename T> void function(T t); and I it to behave a certain way if T has a method g(), and another way if it doesn't. Perhaps there is something that can be used together with boost's enable_if? Something like this: template <typename T> enable_if<has_method<T, g, void ()>, void>::type function(T t) { // Superior implementation calling t.g() } template <typename T> disable_if<has_method<T, g, void ()>, void>::type function(T t) { // Inferior implementation in the case where T doesn't have a method g() } "has_method" would be something that preferably checks both that T has a method named 'g', and that the method has the correct signature (in this case, void ()). Any ideas?

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• PHP OOP: Unique method per argument type?

  - by sunwukung

  I'm writing a little homebrew ORM (academic interest). I'm trying to adhere to the TDD concept as a training exercise, and as part of that exercise I'm writing documentation for the API as I develop the class. Case in point - I'm working on a classic "getCollection" type mapper class. I want it to be able to retrieve collections of asset X (let's say blog posts) for a specific user, and also collections based on an arbitrary array of numeric values. So - you might have a method like any one of these $User = $UserMapper->load(1); $ArticleCollection = $ArticleMapper->getCollection(range(10,20)); $ArticleCollection = $ArticleMapper->getCollection($User); $ArticleCollection = $ArticleMapper->getCollection($User->getId()); So, in writing the documentation for the getCollection method - I want to declare the @param variable in the Docblock. Is it better to have a unique method for each argument type, or is it acceptable to have a method that delegates to the correct internal method/class based on argument type?

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• Extracting methods body from a class of Java Source Code

  - by Muhammad Asaduzzaman

  Hi, I want to extract method body from a Java Source Code. Suppose I have the following code: public class A{ public void print(){ System.out.println("Print This thing"); System.out.println("Print This thing"); System.out.println("Print This thing"); } } My objective is not to extract the method name (in this case print) but also the bode of the method(In this case the three print statement inside the print method). Can anyone suggest how can I do so? Is their any library available for doing so.

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• How see the converted sql from ActiveRecord method in view, etc

  - by Jak

  Hi All, I will be happy if someone clear doubt, i can see objects in view by using <%= debug @object % and lot of methods is there apart from view like .to_yml, etc Is there any method available for seeing the converted sql from ActiveRecord method in view, etc. Although I can find it in console but it will confuse when we run multiple queries.. example: User.find :all it will produce "SELECT * FROM users;" in output console But i want it in view are any other specific point like yml , etc ? Thanks, Jak

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• [C++] Question on Virtual Methods

  - by bobber205

  IF both methods are declared as virtual, shouldn't both instances of Method1() that are called be the derived class's Method1()? I am seeing BASE then DERIVED called each time. I am doing some review for an interview and I want to make sure I have this straight. xD class BaseClass { public: virtual void Method1() { cout << "Method 1 BASE" << endl; } }; class DerClass: public BaseClass { public: virtual void Method1() { cout << "Method 1 DERVIED" << endl; } }; DerClass myClass; ((BaseClass)myClass).Method1(); myClass.Method1(); Method 1 BASE Method 1 DERVIED

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• public (static) swap() method vs. redundant (non-static) private ones...

  - by Helper Method

  I'm revisiting data structures and algorithms to refresh my knowledge and from time to time I stumble across this problem: Often, several data structures do need to swap some elements on the underlying array. So I implement the swap() method in ADT1, ADT2 as a private non-static method. The good thing is, being a private method I don't need to check on the parameters, the bad thing is redundancy. But if I put the swap() method in a helper class as a public static method, I need to check the indices every time for validity, making the swap call very unefficient when many swaps are done. So what should I do? Neglect the performance degragation, or write small but redundant code?

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• Which is the better way to simulate optional parameters in Java?

  - by froadie

  I have a Java method that takes 3 parameters, and I'd like it to also have a 4th "optional" parameter. I know that Java doesn't support optional parameters directly, so I coded in a 4th parameter and when I don't want to pass it I pass null. (And then the method checks for null before using it.) I know this is kind of clunky... but the other way is to overload the method which will result in quite a bit of duplication. Which is the better way to implement optional method parameters in Java: using a nullable parameter, or overloading? And why?

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• Any method to denote object assignment?

  - by Droogans

  I've been studying magic methods in Python, and have been wondering if there's a way to outline the specific action of: a = MyClass(*params).method() versus: MyClass(*params).method() In the sense that, perhaps, I may want to return a list that has been split on the '\n' character, versus dumping the raw list into the variable a that keeps the '\n' intact. Is there a way to ask Python if its next action is about to return a value to a variable, and change action, if that's the case? I was thinking: class MyClass(object): def __init__(*params): self.end = self.method(*params) def __asgn__(self): return self.method(*params).split('\n') def __str__(self): """this is the fallback if __asgn__ is not called""" return self.method(*params)

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• A way to return multiple return values from a method: put method inside class representing return value. Is it a good design?

  - by john smith optional

  I need to return 2 values from a method. My approach is as follows: create an inner class with 2 fields that will be used to keep those 2 values put the method inside that class instantiate the class and call the method. The only thing that will be changed in the method is that in the end it will assign those 2 values to the fields of the instance. Then I can address those values by referencing to the fields of that object. Is it a good design and why?

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• Delegate.CreateDelegate() and generics: Error binding to target method

  - by SDReyes

  I'm having problems creating a collection of delegate using reflection and generics. I'm trying to create a delegate collection from Ally methods, whose share a common method signature. public class Classy { public string FirstMethod<out T1, in T2>( string id, Func<T1, int, IEnumerable<T2>> del ); public string SecondMethod<out T1, in T2>( string id, Func<T1, int, IEnumerable<T2>> del ); public string ThirdMethod<out T1, in T2>( string id, Func<T1, int, IEnumerable<T2>> del ); // And so on... } And the generics cooking: // This is the Classy's shared method signature public delegate string classyDelegate<out T1, in T2>( string id, Func<T1, int, IEnumerable<T2>> filter ); // And the linq-way to get the collection of delegates from Classy ( from method in typeof( Classy ).GetMethods( BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.NonPublic ) let delegateType = typeof( classyDelegate<,> ) select Delegate.CreateDelegate( delegateType, method ) ).ToList( ); But the Delegate.CreateDelegate( delegateType, method ) throws an ArgumentException saying Error binding to target method. : / What am I doing wrong?

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• Bind to a method in WPF?

  - by Cameron MacFarland

  How do you bind to an objects method in this scenario in WPF? public class RootObject { public string Name { get; } public ObservableCollection<ChildObject> GetChildren() {...} } public class ChildObject { public string Name { get; } } XAML: <TreeView ItemsSource="some list of RootObjects"> <TreeView.Resources> <HierarchicalDataTemplate DataType="{x:Type data:RootObject}" ItemsSource="???"> <TextBlock Text="{Binding Path=Name}" /> </HierarchicalDataTemplate> <HierarchicalDataTemplate DataType="{x:Type data:ChildObject}"> <TextBlock Text="{Binding Path=Name}" /> </HierarchicalDataTemplate> </TreeView.Resources> </TreeView> Here I want to bind to the GetChildren method on each RootObject of the tree. EDIT Binding to an ObjectDataProvider doesn't seem to work because I'm binding to a list of items, and the ObjectDataProvider needs either a static method, or it creates it's own instance and uses that. For example, using Matt's answer I get: System.Windows.Data Error: 33 : ObjectDataProvider cannot create object; Type='RootObject'; Error='Wrong parameters for constructor.' System.Windows.Data Error: 34 : ObjectDataProvider: Failure trying to invoke method on type; Method='GetChildren'; Type='RootObject'; Error='The specified member cannot be invoked on target.' TargetException:'System.Reflection.TargetException: Non-static method requires a target.

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• 'Must Override a Superclass Method' Errors after importing a project into Eclipse

  - by Tim H

  Anytime I have to re-import my projects into Eclipse (if I reinstalled Eclipse, or changed the location of the projects), almost all of my overridden methods are not formatted correctly, causing the error 'The method ?????????? must override a superclass method'. It may be noteworthy to mention this is with Android projects - for whatever reason, the method argument values are not always populated, so I have to manually populate them myself. For instance: list.setOnCreateContextMenuListener(new OnCreateContextMenuListener() { public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { //These arguments have their correct names } }); will be initially populated like this: list.setOnCreateContextMenuListener(new OnCreateContextMenuListener() { public void onCreateContextMenu(ContextMenu arg1, View arg2, ContextMenuInfo arg3) { //This methods arguments were not automatically provided } }); The odd thing is, if I remove my code, and have Eclipse automatically recreate the method, it uses the same argument names I already had, so I don't really know where the problem is, other then it auto-formatting the method for me. This becomes quite a pain having to manually recreate ALL my overridden methods by hand. If anyone can explain why this happens or how to fix it .. I would be very happy. Maybe it is due to the way I am formatting the methods, which are inside an argument of another method?

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• Case class copy() method abstraction.

  - by Joa Ebert

  I would like to know if it is possible to abstract the copy method of case classes. Basically I have something like sealed trait Op and then something like case class Push(value: Int) extends Op and case class Pop() extends Op. The first problem: A case class without arguments/members does not define a copy method. You can try this in the REPL. scala> case class Foo() defined class Foo scala> Foo().copy() <console>:8: error: value copy is not a member of Foo Foo().copy() ^ scala> case class Foo(x: Int) defined class Foo scala> Foo(0).copy() res1: Foo = Foo(0) Is there a reason why the compiler makes this exception? I think it is rather unituitive and I would expect every case class to define a copy method. The second problem: I have a method def ops: List[Op] and I would like to copy all ops like ops map { _.copy() }. How would I define the copy method in the Op trait? I get a "too many arguments" error if I say def copy(): this.type. However, since all copy() methods have only optional arguments: why is this incorrect? And, how do I do that correct? By making another method named def clone(): this.type and write everywhere def clone() = copy() for all the case classes? I hope not.

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